Is it though? let's try a little parable; two people, Mr. Starbucks and Mister Nobody set up coffeee shops side by side on the same street in Seattle; with a few months, its clear that Mr. Starbucks has the edge - more customers, better selection, a nicer atmosphere, and Mr. Nobody goes out of business. Fair enough, you say, and i wouldn't argue; competition on equal terms can produce a better outcome for the consumer.
Chapter 2: Mr S decides he'd like to build on his success, so he goes to a bank - or banks - and borrows money to invest in other premises; pretty soon the pattern repeats, and other coffee shops in the neighbourhoods of the new S'bucks go to the wall; except this time its not the fair fight it was in the first instance, because now, with 10 or 20 or 100 shops, Mr. S can buy his raw materials at much better prices, can operate long lines of credit which means the little Mr nobodies up against him cannot compete even if they are producing a better product.
Chapter 3: There's a starbucks on every corner in every major city in the west - they pretty much dictate the price coffee growers get, and, by making themselves into arbiters of taste they start recommending books and music to their customers - and taking a cut from the proceeds. The net effect is to cut down competition and to make it harder to get a decent coffee in some cities if you don't care for the frothy pabulum S'bucks want to sell you - I personally find their presence in Rome deeply depressing.
Or, to pick an example which is probably under your fingers at the moment - I 'm typing this on a PC running windows in UCD; both the hardware and the operating system are worse in every respect than the Mac* I use at home - yet there's a 9 out of 10 chance that you're reading this on the same, inferior system; why? its not cheaper - Linux is - and its certainly not better; its because Capitalism, the system that is supposed to thrive on competition allows the slight edge that we saw in example one to build into massive corporate muscle because, apparently, the market is always right and it is somehow a neutral system like the weather, and interfering with it is a sin against freedom.
BTW, I never said i was against a mixed economy; I basically believe in social ownership of the means of production, but some means of production are too small or specialised for that model to work very well - you must be mixing me up with the other half of the Phibsborough Popular Front for the re-education of Cork.......
* I don't necessarily buy the Apple good, Microsoft bad dualism - but they do make nicer computers.